maybe it is a wossner but an early one. I think the piston is out of a 470 which means that it misses the head by miles.
I do a 450 piston for sure BUT I would run the bike with a flat piston but with perfect squish.
I can't imagine you wanting to ride without the higheest compression but I think the bike is too jerky with a HC piston in it.
I'd rather have a flat piston, DVSK, a jetting kit and the right KIND of power.
regards
Taffy